When it is desired to mount a door or window to pivot both inward and outward, a "center pivot" is commonly used. Center pivots are so called because they are mounted on the horizontal center line of the door midway between and parallel to the inner and outer door surfaces. The most common arrangement for mounting a bottom center pivot is to mount the pivot to an L-shaped bracket, the upright leg of which is fastened to the door frame and the horizontal leg of which rests on the floor. The spindle of the pivot extends upward from the horizontal leg of the L-shaped bracket, and the door is installed on the pivot spindle. In applications which employ a threshold, it is necessary to drill or notch the threshold so that it will clear the pivot spindle.
This type of mounting arrangement, though widely used, suffers certain disadvantages when used in conjunction with a threshold. First, two separate members--the mounting bracket and the threshold--must be installed. Installation is further complicated by the requirement that the L-shaped mounting bracket and the threshold be properly aligned to permit the pivot spindle to clear the cutout in the threshold. Accordingly, there is a need for an improved mounting arrangement for a bottom center pivot when used in conjunction with a threshold.
One approach to this problem has been to mount a bottom center door pivot directly to the threshold. This type of center door pivot is sold by Dorma Door Controls, Inc. and others. This type of pivot assembly comprises a threshold lug which includes a hexagonal head portion and a downwardly extending tubular shaft which is threaded on its interior and exterior surfaces. The shaft of the threshold lug is inserted through a hole in the threshold, and a nut is threaded onto the outer threaded shaft surface from the opposite side of the threshold to clamp the threshold lug in place. A pivot spindle is then threaded into the threshold lug by means of a screw slot formed in the top of the pivot spindle. A lock nut is then threaded over the pivot spindle and tightened against the head of the threshold lug to prevent the pivot assembly from turning. The door with its associated bearings is then installed onto the pivot spindle.
While this approach eliminates the need for a separate mounting bracket, this type of mounting arrangement suffers its own disadvantages. Because of the requirement that the head portion of the threshold lug and the lock nut both sit atop the threshold and the spindle project above both of these elements, this type of adjustable threshold pivot set extends a considerable distance above the upper surface of the threshold. Consequently, a door with a standard 21/32" inch web cannot be used with this type of pivot arrangement. Rather, a door with a 1-9/16" deep web must be used. Further, since the tool engaging portion of the pivot spindle is a screw slot in the top of the spindle, the door must be removed from the spindle to access the screw slot to adjust the height of the pivot.
Thus, there is a need for an adjustable center pivot which can be mounted directly to a threshold and can accommodate a standard 21/32" web.
There is a further need for an adjustable center pivot which can be mounted directed to the threshold and which permits height adjustment without having to remove the door from the pivot.